The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Distributed process control systems, like those used in chemical, petroleum or other process plants, typically include one or more process controllers communicatively coupled to one or more field devices via analog, digital or combined analog/digital buses, or via a wireless communication link or network. The field devices, which may be, for example, valves, valve positioners, switches, and transmitters (e.g., temperature, pressure, level and flow rate sensors), are located within the process environment and generally perform physical or process control functions such as opening or closing valves, measuring process parameters, etc. to control one or more process executing within the process plant or system. Smart field devices, such as field devices conforming to the well-known Fieldbus protocol may also perform control calculations, alarming functions, and other control functions commonly implemented within the controller. The process controllers, which are also typically located within the plant environment, receive signals indicative of process measurements made by sensors and/or field devices and/or other information pertaining to the field devices and execute a controller application that runs, for example, different control modules that make process control decisions, generate control signals based on the received information and coordinate with the control modules or blocks being performed in the field devices, such as HART®, Wireless HART®, and FOUNDATION® Fieldbus field devices. The control modules in the controller send the control signals over the communication lines or links to the field devices to thereby control the operation of at least a portion of the process plant or system.
Information from the field devices and the controller is usually made available over a data highway to one or more other hardware devices, such as operator workstations, personal computers or computing devices, data historians, report generators, centralized databases, or other centralized administrative computing devices that are typically placed in control rooms or other locations away from the harsher plant environment. Each of these hardware devices typically is centralized across the process plant or across a portion of the process plant. These hardware devices run applications that may, for example, enable an operator to perform functions with respect to controlling a process and/or operating the process plant, such as changing settings of the process control routine, modifying the operation of the control modules within the controllers or the field devices, viewing the current state of the process, viewing alarms generated by field devices and controllers, simulating the operation of the process for the purpose of training personnel or testing the process control software, keeping and updating a configuration database, etc. The data highway utilized by the hardware devices, controllers and field devices may include a wired communication path, a wireless communication path, or a combination of wired and wireless communication paths.
A distributed process control system can include one or more remote terminal units (RTUs), which can be implemented flow computers coupled to field devices. Accordingly, RTUs sometimes are referred to as “flow computers” or simply “controllers.” An RTU can include, for example, an I/O module for connecting to wired Highway Addressable Remote Transducer (HART) field devices and an I/O module for connecting to wireless HART field device. A machine host that implements a supervisory control and data acquisition system, such as an asset management system (AMS), can communicate with one or more RTUs to collect information regarding field devices connected to the RTUs. In some cases, a HART server, which can be implemented in a separate dedicated host, provides an interface to HART field devices. The AMS and the HART server can operate according to a Remote Access Service (RAS) scheme. For example, the AMS can interact with network interface for RAS using RAS Host System Interface (HSI). The AMS can connect with the RAS HART server via multiple Ethernet ports, to pass different types of data and/or commands.
One of the purposes for which an AMS can collect information about field devices from an RTU is constructing a complete hierarchy of field devices, including determining device identities, parent-child relationships, etc. The AMS can then generate a visualization and/or a text description of the hierarchy for the operator of the host machine. For devices that communicate using the HART protocol (“HART devices”), the AMS can request device hierarchy information via a HART server, which generally sends a sequence of HART commands to each device to collect the necessary information. More particularly, the sequence can include command #0 to retrieve device identity, command #13 to retrieve the so-called short tag, specifies describes certain parameters of the device, and, for some devices, command #20 to retrieve the so-called long tag, which describes additional parameters of the device. The step of collecting this information can take eight to 12 second per HART device to collect the necessary information. For wireless HART devices operating in a large mesh network, this step can take even longer.
As a result, building the entire device hierarchy for an RTU is a time-consuming operation, and the duration depends to a large extent on the number of connected HART devices.